I feed my girls crushed red peppers, they cannot taste the heat, It makes the yolks a nice orange color. Marigolds work too, but some research says it may reduce egg production. Not all the girls eat the crushed hot peppers, but the ones that do have a big color difference. This was to answer the question of egg color only, I know folks will jump at this opportunity to let you know their feelings about everything I did not say because that's what some of these folks like to do. I know the color has NOTHING to do with the quality. I think you should feed your chickens the best diet you can, but to answer the color question, crushed chili peppers will work and not harm your girls in any way. Happy Chicken Keeping!